Update header files to match source files (#2143)

include/time_events.h

@@ -1,8 +1,8 @@
 #ifndef GUARD_TIME_EVENTS_H
 #define GUARD_TIME_EVENTS_H
 
-void UpdateMirageRnd(u16);
-u8 IsMirageIslandPresent(void);
-void UpdateBirchState(u16);
+void UpdateMirageRnd(u16 days);
+bool8 IsMirageIslandPresent(void);
+void UpdateBirchState(u16 days);
 
 #endif // GUARD_TIME_EVENTS_H